In recent years, a so-called MEMS technology has been developed for fabricating highly functional devices such as sensors and actuators in μ-sizes by utilizing a high precision three-dimensional machining technology based on semiconductor production technology. By utilizing the MEMS technology, further, there has also been proposed a very small oscillating current converter capable of taking out an electric current by converting oscillation occurring on a cantilever into electric energy (see, for example, patent document 1 and non-patent document 1).
Of them, the following non-patent document 1 discloses an oscillating current converter 300 as shown in FIG. 21. The oscillating current converter 300 includes a plurality of cantilevers 302 cantilevered via a support portion 301, coils 303 formed on the surfaces of the cantilevers 302, and a magnet 304 arranged near the cantilevers 302. The oscillating current converter 300 has the cantilevers 302 which are arranged in the same direction and in parallel with each other having lengths that are successively differing so that the cantilevers 302 oscillate at different natural frequencies. In the oscillating current converter 300, the cantilevers 302 oscillate so as to generate induced electromotive forces in the coils 303.
According to the oscillating current converter 300 disclosed in the non-patent document 1, however, the distance is not the same between the cantilevers 302 and the magnet 304 arousing such a problem that a difference occurs in the electromotive force produced in the coils 303 arranged on the cantilevers 302. The oscillating current converter 300 further has a problem in that the device as a whole becomes bulky depending upon the size of the magnet 304.
In order for the oscillating current converter 300 to produce a large electromotive force, further, it can be contrived to increase a change in the magnetic flux by, for example, increasing the natural frequencies and amplitudes of the cantilevers 302. With the conventional oscillating current converter 300, however, it is difficult to increase the amplitudes of the cantilevers 302. If, for example, the lengths of the cantilevers 302 are increased to increase the amplitudes of the cantilevers 302, then the device becomes bulky as described above.
[Patent document 1] JP-A-7-107752
[Non-patent document 1] Ibrahim Sari, Tuna Balkan and Haluk Kulah, “A WIDEBAND ELECTROMAGNETIC MICRO POWER GENERATOR FOR WIRELESS MICROSYSTEMS”, Transducer & EUROSENSORS '07, p. 275-278